Particles of material are coated for various reasons. Sand for use in fracking and the like is coated with dust suppressant. Sand used for fracking is coated by spraying it with a dust suppressant as it is conveyed over the end of a conveyor and into a waiting truck.
Other materials are often coated in rotating drums called tumblers, in which particles are sprayed with coating solutions as they cascade off of baffles located in the tumbler. See e.g. U.S. Pat. Nos. 4,478,171 and 3,991,225. Agglomerators in which particles are agglomerated by spraying with water or an agglomerating solution are similar. See e.g. U.S. Pat. Nos. 4,507,335 and 4,353,852.
In U.S. Pat. No. 4,921,674, seeds are sprayed with chemicals by laterally directed nozzles as they cascade over baffles in a tower. In U.S. Pat. Nos. 4,369,689 and 6,106,753, particles are coated by downwardly directed nozzles as they fall through a delivery chute. In '689, a cone shaped baffle is positioned above the downwardly directed nozzle.